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Limitations of adaptive signals Limitations of adaptive signals

Limitations of adaptive signals - PowerPoint Presentation

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Uploaded On 2017-09-03

Limitations of adaptive signals - PPT Presentation

David Hale Leidos preview Ineffective heuristic methods Ineffective at certain congestion levels Lack of accountability Low market share Competing technologies Heuristic methods ASCTs optimize complex networks in only a few seconds ID: 584893

effective adaptive signals methods adaptive effective methods signals saturation experience technologies share market time asct decades tool products good analysis demand optimize

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Slide1

Limitations of adaptive signals

David Hale (Leidos)Slide2

preview

Ineffective heuristic methodsIneffective at certain congestion levelsLack of accountability

Low market shareCompeting technologiesSlide3

Heuristic methods

ASCT’s optimize complex networks in only a few seconds.

Is this enough time to produce a good solution?Or, is it only enough time to produce a “quick and dirty” solution?Industrial engineering experts would not be impressed.

Fast Methods (not effective)

Equisat

Webster’s method

Greedy algorithmHill-climbingSlow Methods (effective)Simulated annealingEvolutionary algorithmsDerivative-free methodsSlide4

y

z

x

Run Time

Delay Reduction

A

B

CSlide5

Adapting vs. optimizing

(none)

Non-Adaptive,

Quasi-Adaptive

Fully Adaptive

Quick Optimization

Thorough OptimizationSlide6

Degree of saturation

“If geared toward sporadic demand, they’re effective. In corridors with defined peaks and aggressive timing, they experience diminishing returns.”

Delay

Degree of Saturation

0.80

1.00Slide7

accountability

“The industry needs a tool to quantify myriad adaptive products.”

“People are implementing these systems without a real analysis.”

Proprietary, secret algorithms

Capacity

analysis? NO

Simulation? DIFFICULT

Most products can’t do it

VISSIM API = extra $$$Too much time, money, expertiseSlide8

accountability

There is just way too much marketing.”Advertising

over

science?

Capitalism, good and bad

Cherry-picked case studies

67

% said ASCT was good for oversaturated conditionsLaw & OrderITE Community discussion on ASCTExperts with decades of signal experienceASCT is just “one tool in the toolbox”

ASCT “has its place”Slide9

Market share

“With less than 5% market share after 5 decades, acceptance is not consistent with successful technologies.”

“Adaptive control in its infancy?”Decades of availability (1960’s)

SCATS (1976), SCOOT (1981)

Fewer than 5% of signals are adaptive

Why?

Costs too high

Uncertainty about benefitsSlide10

Competing technologies

“Automated performance measures allow agencies to optimize and manage signals without an adaptive system.”

Data drivenQuasi-adaptive

Stronger algorithmsSlide11

Recent quotes

“The industry needs a tool to quantify myriad adaptive products.”

“People are implementing these systems without a real analysis.”“If geared toward sporadic demand, they’re effective. In corridors with defined peaks and aggressive timing, they experience diminishing returns.”

“We only use them when other options have failed.”

“There is just way too much marketing.”

“Clearly the jury is out on where they should be deployed.”

“From my experience it is smoke and mirrors.”

“With less than 5% market share after 5 decades, acceptance is not consistent with successful technologies.”

“Automated performance measures allow agencies to optimize and manage signals without an adaptive system.”Slide12

My current opinion

Traffic too light = not cost effective

Delay not sensitive below 80% saturationTraffic too heavy = not cost

effective

Everything is pre-timed over 120% saturation

No platoon progression

Cycle, offsets, phasing sequence insignificant

Traffic medium = sometimes cost effective

Sporadic demand (movie theater, football stadium)Unpredictable pedestrian activityEmergency vehiclesIncidents / accidentsSlide13

Limitations of adaptive signals

David Hale (Leidos)